Readymade gluten free and dairy free foods.

Buy Gluten Free (GF) soy sauce.
Daiya fake cheeses, cheesecake, and pizzas.
Udi breads and rolls
Vitamin B-12 since you need real milk sugar to manufacture it on your own. Pills or injections. Injections are best since you can build up three years of storage in the liver and there isn't any issue with absorption. Pure sublingual B-!2 from Trader Joe's or health food store is second best.
Electric pressure cooker and air frier to make your own rice and fried foods using GF bread crumbs or GF panko crumbs.
Microwave to heat frozen foods and freshen GF baked goods (which are often sold frozen).
Ask your grocery store for a list of all their GF foods. Also buy online. There are ice cream cones, cakes, etc.